It depends on the year of the car.....but if you are running HEI ignition (74 and later) it will run to the carb. It goes to a ported vacuum signal. You will find a ported vacuum on a fitting that is above the carb base plate. It should have no vacuum when the engine is idling but will have vacuum when you rev the engine.
If you have a manual transmission and a centrifugal advance distributor, you don't have any. If you have vacuum advance on your distributor, there's one vacuum hose running from the side of the carb to the distributor. If you have an automatic transmission, you've got a hose from the intake manifold to the control valve.
you need manifold vacuum. Either on one of the intake runners or at the base of the carb.
There should be a vacuum source on the carb above the throttle body that gives spark ported vacuum. You can connect a tube from this source to the distributor.
If it is a point type distributor you will want to hook it to constant vacuum...somewhere on a port in the base plate. If it's HEI you'll want to hook it to one in the carb body. Something that has no vacuum at idle but pulls vacuum as you give it throttle.
This must be a vacuum hose, with a connection to the intake manifold, at rear of carb. This must be an after-market distributor because the original "Lean Burn" computer did not have a vacuum advance distrib. The vacuum was connected to the computer that controlled the distrib. advance. these setups, one made by Mopar, kit #P3690426, by passed the computer and is vacuum operated.
There should be two small and one large vacuum connection points on the front of the carb, hook it to one of the small ones, that will be for your vacuum advance. the big one is for crankcase ventilation. one of the smaller ports is manifold vacuum, the other is timed vacuum. they are not the same, but you will use one of these, usually the "timed" port.
vacuum lines,there are three one for each petcock and one for the vacuum advance, the two for the petcocks go to the carb boots, one on each side,and the one for the vacuum advance goes directly to the no. two carb.
Your distributor needs vacuum to advance your timing during acceleration. That's why you hook up your line to the port that has no vacuum at idle. :O)
Check your timing and your vacuum advance.
Look on the carb for a small vacuum source above the throttle body. You would want one that has no vacuum at idle.
Depending on your carb, distributor and transmission, you have from zero to two vacuum hoses. If you have an Autostick transmission, there's a vacuum hose running from a port in the intake manifold to the control valve on the left side wall of the engine bay. (Hint: if you've got a car that came with Autostick and that someone's converted to manual transmission, the bracket for the control valve is the perfect place for your coil.) Most people don't have this transmission even if their car came with it--it's only a three-speed and it's hard to find parts for it, so most of those cars have been converted to manual transmission. The other hose you might have is for your distributor. The port is on the left side of the carb, and a hose runs between it and the metal vacuum advance can on the side of the distributor. If you have a 009 distributor or an aftermarket distributor like an MSD you don't have the vacuum advance can; if you have an aftermarket carb like a Weber you don't have the port. Therefore...you probably don't have any vacuum lines on your engine.
Any place that has constant vacuum Usually on the back side at the base of the carb.